Area Forecast Discussion
Issued by NWS Medford, OR

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FXUS66 KMFR 011052

Area Forecast Discussion
National Weather Service Medford OR
352 AM PDT SAT OCT 1 2016

.DISCUSSION...An upper level trough and associated short wave will
move onshore this morning. As of 330 am PDT, satellite and radar
imagery are both showing showers and isolated thunderstorms over
the coastal waters and along the coast, extending inland to
Josephine and Douglas Counties. These will move through
Roseburg/Grants Pass in the next couple of hours and one or two
may also move over Medford/Ashland this morning or early this
afternoon. The initial short wave will lift northeast of the area
later this morning and there will likely be some sunny breaks at
times, especially from the Rogue Valley east and south. Onshore
flow will keep more clouds and the best shower chances along the
coast with high temperatures right around normal for early
October. Inland high temperatures, however, will be about 6-12
degrees below average. That means mostly upper 60s in Roseburg,
Medford, Grants Pass and Yreka with upper 50s to lower 60s in
Klamath Falls and Alturas.

Tonight into Sunday, another deeper upper level disturbance will
dive southward along the PacNW coast. This one will generate a
nice band of precipitation along the coast that will move inland
Sunday morning. Widespread wetting rainfall is likely across all
of the west side during this time frame. Rain amounts of 1-2 inches
are likely along the coast with some higher amounts in the Coast
Range. Overall, the west side valleys will have 0.25-0.50 of an
inch. Snow levels will drop to about 5500 feet with a few inches
of snow possible in the Cascades, especially at the rim at Crater
Lake. The H5 cold pool (-26C) will move overhead Sunday afternoon
and precipitation will become more showery. Due to the cold air
aloft though, pretty much anywhere across the CWA will be unstable
enough to crack out a lightning strike or two, so have introduced
a slight chance of thunderstorms to the forecast.

Sunday night into Monday morning, showers will gradually taper
off and end as the best forcing shifts off to the east. Showers
will probably linger longest near the mountains and also over far
eastern sections.

Monday afternoon into Tuesday, models continue to indicate another
disturbance moving in from the Pacific. There is general model
agreement that this system will bring some rain to the forecast
area, but disagreement in the timing and placement of the
steadiest rainfall. Most of the guidance is bringing a decent area
of isentropic lift and warm advection precipitation through the
area Monday night, then shifting it to the east by Tuesday
morning. The EC is a bit of an outlier as it skirts the south and
west part of the CWA, preferring to keep the best forcing in
northern California. For now, have gone with likely POPs along
the coast and in the mountains with chance POPs elsewhere with the
idea that we`ll fine tune the details in coming shifts. Overall
though, this system won`t produce as much rain as the one
Saturday night into Sunday.

Tuesday night through Thursday morning, expect a gradual shift in
precipitation chances back to the north and west as an upper ridge
gradually builds and shifts across the area. Areas south and east
of the Cascades will dry out and even areas north and west
probably do too for a while. However, the next front will likely
move into the area Thursday into Friday. -Spilde


.AVIATION...01/06Z TAF CYCLE...Over the coastal waters...along the
coast...and in the Umpqua Basin...CIGS will be mainly VFR with
isolated MVFR cigs and mountain obscuration in rain showers through
Saturday afternoon. Coastal conditions are likely to worsen during
Saturday evening with areas of MVFR and the arrival of rain that
will be locally moderate in intensity.

Over the remainder of the area...VFR conditions will prevail through
Saturday evening...but some higher terrain will be obscured from
early Saturday morning into Saturday afternoon.

Note: The ceilometer at FAA site KOTH is out of service, so there
will be no ceiling observations available between 04Z and 14Z. /DW


.MARINE...Updated 300 AM PDT Saturday 1 October 2016...Low
pressure will sweep across the waters this morning with isolated
thunderstorms. A cold front will bring strong south winds through
tonight. Low pressure lingers over the waters Sunday then another
front will arrive late Monday. Steep swell will likely follow Monday
night into Wednesday. Sven


.FIRE WEATHER...Updated 300 AM PDT Friday 30 September
2016...The newest model suite shows little change in the forecast
for today. Although most areas will continue to see humidity values
rise, a dry slot is expected to mix down to the surface this
afternoon. This will help keep humidity values slightly lower with
higher winds across the East Side today.

Confidence remains moderate for wetting rains for areas from the
Cascades west on Sunday. A cool and unsettled pattern remains
through the weekend into the early part of next week. A weak upper
ridge builds over the region for the middle of next week with brief
warming and drying before changing back to an upper trough pattern
with cooling and unsettled weather returning. Sven




Pacific Coastal Waters...Small Craft Advisory from 2 PM this afternoon
     to 5 AM PDT Sunday for PZZ350-356-370-376.


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